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felix Asked :Hi I recently purchased the QS-V27179 MFC CODE: XLSP from you. It all works fine except that the shower head won't turn on unless you first use the body jets or handheld sprayer. Flova UK tells me this could be because it requires a universal pump whereas I have a Stuart Turner positive head pump. Are you familiar with this at all? I can find nothing in the technical literature about any of this regards Felix
Answered By QS Team :
Based on your description, it does sound like you haven’t got enough pressure before the flow switch activates on your pump when operating the rainshower.
It isn’t as black and white as to whether a positive head pump will or won’t work, unfortunately. There are many factors such as the positioning of the water storage, pipework size and bends, positioning of the shower head itself etc. which determine whether a positive head pump is compatible. A negative head and the universal pump are guaranteed to work on every product because they do not rely on a flow switch. A positive head pump can be used where the cold water tank is above the rainshower.
Please see below illustration of the ideal positive head installation which I have taken from the internet. In a positive head pump installation, the product relies on the gravity-fed system to produce enough flow rate through the outlet. How this is worked out, is per meter high the bottom of the tank is away from the top of the rainshower equals 0.1 bar of pressure. E.g. 2 meter distance = 0.2 bar. Illustration.
The product XLSP is a high-pressure product which requires a minimum of 1.0 bar pressure to operate. I would say at a minimum, you’d need at least 0.5 bar to operate the flow switch which means the bottom of the tank would need to be 5 meters away from the rain shower. However, because the product requires 1.0 bar pressure then it is likely you would need even more meter head to have enough flow rate to operate the flow switch. Unfortunately, we have no way to increase the flow rate to the rainshower enough to operate the flow switch.